WO2024045797A1 - Non-isolated resonant converter - Google Patents

Abstract

Provided in the present invention is a non-isolated resonant converter. The non-isolated resonant converter comprises a first resonant bridge, a second resonant bridge, a freewheeling diode unit, a resonant network, an autotransformer, a load, and an output capacitor, wherein the autotransformer comprises a first transformer inductor, a second transformer inductor, and a third transformer inductor. Therefore, a simple circuit, simple and easy control, and low cost are realized.

Description

Non-isolated resonant converter

This application requires the priority of a Chinese patent application with a filing date of August 30, 2022, an application number of 2022110493809, and an invention titled "Non-Isolated Resonant Converter". The contents of the above application are incorporated herein by reference.

Technical field

The present invention relates to the field of power supply technology, and in particular, to a non-isolated resonant converter.

Background technique

In recent years, with the increase in computing volume, the power demand of server single boards has become larger and larger. Especially with the widespread use of rack-mounted servers, the current of the DC power supply bus has become larger and larger. The 48V bus is used to power server boards. The power supply architecture gradually replaces the traditional architecture of the 12V bus; this 48V architecture usually converts the AC grid power into a 48V DC bus through the AC power supply, and then converts the 48V to 12V by the DCDC power supply, and then converts the 12V to what each chipset requires. Various voltages as low as 0.6V are used to power the chipset. There are also some solutions that directly convert 48V into a CPU core voltage of about 1V to power the CPU. Since in server systems, in addition to each chipset requiring low-voltage power supply as low as 0.6V, there are also many 12V loads, such as fans and memory. The method of converting 48V to 12V and then converting 12V to voltage to power the chipset has gradually become mainstream.

On the one hand, the server market is huge and the cost pressure is high; on the other hand, the global requirements for energy conservation and consumption reduction are getting higher and higher, which makes low-cost and high-efficiency 48V to 12V conversion a very important research in the field of power electronics. direction, many research resources go into In this field, many research results have been presented one after another. There are two technical directions that have been most widely used: One direction is to continuously optimize the design based on the 48V to 12V module power supply that is widely used in the traditional communication field. In recent years, new products have been launched in this direction, and power density and efficiency have also improved year by year; most leading companies use isolated half-bridge or full-bridge hard switching circuits, and a few use isolated half-bridge or full-bridge LLC non-isolated resonance Converter circuit; in order to achieve higher efficiency and power density, this development direction continues to increase the number of layers and copper thickness of PCB boards, constantly optimize the design of isolation transformers, and select power MOS tubes with better performance. The consequences of this are Continuously pushing up the cost of products, lengthening the development cycle, increasing design difficulty and technical requirements for technicians have made the development in this direction reach a bottleneck, making it difficult to continue to balance development between performance and price. The other direction is non-isolated 48V to 12V applications, and the corresponding switched energy storage converter non-isolated resonant converter (Switched Tank Converters, STC) was first introduced, as shown in Figure 6. This converter is cascaded through a multi-stage resonant circuit, which can realize soft switching of all switching devices, and the stress of the switching devices is effectively controlled through the series connection of the switching devices and the output voltage clamping, so that the efficiency of the converter is at a lower level. The cost has been very effectively improved, making this circuit a hot spot in the research field. However, this circuit also has two inherent shortcomings: first, the converter is a resonant scheme of a switched capacitor circuit, the relationship between the input and output voltages is a fixed transformation ratio, and voltage regulation cannot be performed, which greatly limits the application of the converter, especially in After several leading companies successively shifted their server power supply solutions to 12V voltage controllable, the attention of this circuit began to decline; in addition, there are many switching devices and complex control. The series connection of multiple switching devices makes the driving scheme and auxiliary source design complex. Without In the case of a dedicated analog controller, the implementation and cost of the circuit are pushed up, which also limits the application of the circuit to a certain extent. between this Later, the buck converter circuit as shown in Figure 7 attracted attention again. This circuit added a series capacitor to the traditional buck converter circuit. Due to the existence of this capacitor, the duty cycle of the converter can be expanded and the polarity can be increased. It greatly reduces the voltage ripple in front of the output filter inductor and improves the working conditions of the filter inductor, allowing the converter to lower the switching frequency, reduce switching losses, and improve efficiency. At the same time, the circuit structure of the converter is simpler than that of the STC circuit. , reducing the design difficulty. This circuit is a relatively optimized solution for current non-isolated 48V to 12V applications. The only drawback to this circuit is the hard switching. Since the switching device is in a hard switching condition during operation, it limits the increase in the switching frequency of the converter to a certain extent, which limits the module from further improving the power density of the power module.

Therefore, it is necessary to provide a new type of non-isolated resonant converter to solve the above problems existing in the existing technology.

Contents of the invention

The purpose of the present invention is to provide a non-isolated resonant converter to reduce control difficulty and cost.

In order to achieve the above object, the non-isolated resonant converter of the present invention includes a first resonant bridge, a second resonant bridge, a freewheeling tube unit, a resonant network, an autotransformer, a load and an output capacitor. The autotransformer includes The first transformer inductor, the second transformer inductor and the third transformer inductor. The resonant network and the first transformer inductor are connected in series to form a transformer resonant unit. The first end of the transformer resonant unit is connected to the first resonant bridge. connection, the second end of the transformer resonant unit is connected to the second resonant bridge, the same-name end of the second transformer inductor is connected to the different-name end of the third transformer inductor, one end of the output capacitor, One end of the load is connected, the opposite end of the second transformer inductor is connected to the first resonant bridge and the freewheeling tube unit, the same end of the third transformer inductor is connected to the second resonant bridge and The freewheeling tube unit is connected, the first resonant bridge and the second resonant bridge are also connected to the positive electrode of the power supply, and the freewheeling tube unit is connected to the other end of the output capacitor and the other end of the load. and grounded, the first resonant bridge is used to connect the first end of the transformer resonant unit with the positive electrode of the power supply or the freewheeling tube, and the second resonant bridge is used to connect the second end of the transformer resonant unit. The freewheeling tube is used to connect the opposite end of the second transformer inductor or the same end of the third transformer inductor to the other end of the load, where , the number of turns of the first transformer inductor is greater than or equal to 0.

The beneficial effect of the non-isolated resonant converter is that it includes a first resonant bridge, a second resonant bridge, a freewheeling tube unit, a resonant network, an autotransformer, a load and an output capacitor. The autotransformer includes a first transformer inductor. , the second transformer inductor and the third transformer inductor, the circuit is simple, the control is simple and easy, and the cost is low.

Optionally, the first resonant bridge includes a first switch unit and a third switch unit, the first terminal of the first switch unit is connected to the positive pole of the power supply, and the second terminal of the first switch unit is connected to the third switch unit. The first end of the three switch units is connected, and the second end of the third switch unit is connected to the opposite end of the second transformer inductor.

Optionally, both the first switch unit and the third switch unit are controllable switching devices.

Optionally, the second resonant bridge includes a second switching unit and a fourth switching unit, so The first end of the second switch unit is connected to the positive electrode of the power supply, the second end of the second switch unit is connected to the first end of the fourth switch unit, and the second end of the fourth switch unit is connected to the The same terminal of the third transformer inductor is connected.

Optionally, both the second switch unit and the fourth switch unit are controllable switching devices.

Optionally, the freewheeling tube unit includes a fifth switching unit and a sixth switching unit. The first end of the fifth switching unit is connected to the opposite end of the second transformer inductor. The fifth switching unit The second end of the sixth switching unit is connected to the other end of the load, the first end of the sixth switching unit is connected to the same end of the third transformer inductor, and the second end of the sixth switching unit is connected to the end of the load. Connect the other end.

Optionally, both the fifth switching unit and the sixth switching unit are uncontrollable switching devices or controllable switching devices.

Optionally, the controllable switching device includes a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor, a gallium nitride transistor, a silicon carbide MOS transistor, and a first combined switching unit, and the first combined switching unit is a triode. combination with diodes.

Optionally, the uncontrollable switching device includes a diode and a second combined switch unit, and the second combined switch unit includes a diode and a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor, a gallium nitride transistor, and a silicon carbide Any combination of MOS tubes.

Optionally, the resonant network includes a first resonant inductor and a resonant capacitor, and the first resonant inductor, the resonant capacitor and the first transformer inductor are connected in series.

Optionally, the resonant network further includes a resistor, the resistor is connected to the first resonant circuit The inductor, the resonant capacitor and the first transformer inductor are connected in series.

Optionally, the autotransformer further includes a second resonant inductor. When the number of turns of the first transformer inductor is greater than 0, the second resonant inductor is connected in parallel with the first transformer inductor. When the first transformer inductor has When the number of turns of the transformer inductor is equal to 0, the second resonant inductor is connected in parallel with the second transformer inductor.

Optionally, when the number of turns of the first transformer inductor is greater than 0, the first transformer inductor includes at least one sub-transformer inductor, and the sub-transformer inductors are connected in series.

Description of drawings

Figure 1 is a circuit schematic diagram of a non-isolated resonant converter in some embodiments of the present invention;

Figure 2 is a schematic circuit diagram of a non-isolated resonant converter in some embodiments of the present invention;

Figure 3 is a schematic circuit diagram of a non-isolated resonant converter in other embodiments of the present invention;

Figure 4 is a schematic circuit diagram of a non-isolated resonant converter in some embodiments of the present invention;

Figure 5 is a timing diagram of the non-isolated resonant converter shown in Figure 1 in some embodiments of the present invention;

Figure 6 is a circuit schematic diagram of an STC non-isolated resonant converter in the prior art;

FIG. 7 is a circuit schematic diagram of a buck conversion circuit in the prior art.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the following will be combined with the present invention. The accompanying drawings clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention. Unless otherwise defined, technical or scientific terms used herein shall have their ordinary meaning understood by one of ordinary skill in the art to which this invention belongs. The use of "comprising" and similar words herein means that the elements or things appearing before the word include the elements or things listed after the word and their equivalents, without excluding other elements or things.

In order to solve the problems existing in the prior art, embodiments of the present invention provide a non-isolated resonant converter. Referring to Figure 1, the non-isolated resonant converter 100 includes a first resonant bridge 101, a second resonant bridge 102, a freewheeling tube unit 103, a resonant network 104, an autotransformer 105, a load Ro and an output capacitor Co. The coupling transformer 105 includes a first transformer inductor N1, a second transformer inductor N2 and a third transformer inductor N3, wherein the number of turns of the first transformer inductor N1 is greater than 0.

In some embodiments, the resonant network and the first transformer inductor are connected in series to form a transformer resonant unit. The first end of the transformer resonant unit is connected to the first resonant bridge, and the second end of the transformer resonant unit is connected to the first resonant bridge. The end is connected to the second resonant bridge, the same-name end of the second transformer inductor is connected to the opposite-name end of the third transformer inductor, one end of the output capacitor, and one end of the load. The second transformer inductor The opposite end of the inductor is connected to the first resonant bridge and the freewheeling tube unit, the same end of the third transformer inductor is connected to the second resonant bridge and the freewheeling tube unit, the first resonant The bridge and the second resonant bridge are also connected to the positive electrode of the power supply, and the freewheeling tube unit is connected to the other side of the output capacitor. end and the other end of the load are connected and grounded, the first resonant bridge is used to connect the first end of the transformer resonant unit with the positive electrode of the power supply or the freewheeling tube, and the second resonant bridge is used to connect The second end of the transformer resonant unit is connected to the positive electrode of the power supply or the freewheeling tube. The freewheeling tube is used to connect the different-named end of the second transformer inductor or the same-named end of the third transformer inductor. The other end of the load is connected.

In some embodiments, the first resonant bridge includes a first switch unit and a third switch unit, the first terminal of the first switch unit is connected to the positive pole of the power supply, and the second terminal of the first switch unit is connected to the The first end of the third switch unit is connected, and the second end of the third switch unit is connected to the opposite end of the second transformer inductor.

In some embodiments, the second resonant bridge includes a second switch unit and a fourth switch unit, a first terminal of the second switch unit is connected to the positive pole of the power supply, and a second terminal of the second switch unit is connected to the The first end of the fourth switching unit is connected, and the second end of the fourth switching unit is connected to the same end of the third transformer inductor.

In some embodiments, the freewheeling tube unit includes a fifth switch unit and a sixth switch unit. The first end of the fifth switch unit is connected to the opposite end of the second transformer inductor. The fifth switch The second end of the unit is connected to the other end of the load, the first end of the sixth switching unit is connected to the same end of the third transformer inductor, and the second end of the sixth switching unit is connected to the load. the other end of the connection. .

In some embodiments, the first switch unit, the second switch unit, the third switch unit and the fourth switch unit are controllable switching devices, and the fifth switch unit and the sixth switch unit are controllable switching devices. The switching units are all uncontrollable switching devices or controllable switching devices. specifically, The controllable switching device includes a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor, a gallium nitride transistor, a silicon carbide MOS transistor, and a first combined switch unit. The first combined switch unit is a combination of a triode and a diode. , the uncontrollable switching device includes a diode and a second combined switch unit. The second combined switch unit includes a diode and a metal oxide semi-field effect transistor, an insulated gate bipolar transistor, a gallium nitride transistor, or a silicon carbide MOS transistor. Any combination.

Referring to Figure 1, the first switching unit is a first NMOS transistor S1, the second switching unit is a second NMOS transistor S2, the third switching unit is a third NMOS transistor S3, and the fourth switching unit is The fourth NMOS transistor S4, the fifth switching unit is the fifth NMOS transistor S5, and the sixth switching unit is the sixth NMOS transistor S6.

Referring to Figure 1, the drain of the first NMOS transistor S1 is connected to the positive electrode of the power supply, the source of the first NMOS transistor S1 is connected to the drain of the third NMOS transistor S3, and the drain of the third NMOS transistor S3 is connected. The source is connected to the opposite terminal of the second transformer inductor N2.

Referring to Figure 1, the drain of the second NMOS transistor S2 is connected to the positive electrode of the power supply, the source of the second NMOS transistor S2 is connected to the drain of the fourth NMOS transistor S4, and the drain of the fourth NMOS transistor S4 is connected. The source is connected to the same terminal of the third transformer inductor N3.

Referring to Figure 1, the drain of the fifth NMOS transistor S5 is connected to the opposite end of the second transformer inductor N2, and the source of the fifth NMOS transistor S5 is connected to the other end of the load Ro and the output The other end of the capacitor Co and the source of the sixth NMOS transistor S6 are connected to ground, and the drain of the sixth NMOS transistor S6 is connected to the same terminal of the third transformer inductor N3.

In some embodiments, the gate of the first NMOS transistor is connected to the first control signal, the gate of the second NMOS transistor is connected to the second control signal, and the gate of the third NMOS transistor is connected to the third control signal. The gate of the fourth NMOS transistor is connected to the fourth control signal, the gate of the fifth NMOS transistor is connected to the fifth control signal, and the gate of the sixth NMOS transistor is connected to the sixth control signal.

In some embodiments, the resonant network includes a first resonant inductor and a resonant capacitor, and the first resonant inductor, the resonant capacitor and the first transformer inductor are connected in series.

In some embodiments, the resonant network further includes a resistor, the resistor is connected in series with the first resonant inductor, the resonant capacitor, and the first transformer inductor.

Referring to Figure 1, the resonant network 104 includes a first resonant inductor Lr and a resonant capacitor Cr. One end of the resonant capacitor Cr is connected to the source of the first NMOS transistor S1, and the other end of the resonant capacitor Cr is connected to the source of the first NMOS transistor S1. One end of the first resonant inductor Lr is connected, the other end of the first resonant inductor Lr is connected to the same-name end of the first transformer inductor N1, and the opposite-name end of the first transformer inductor N1 is connected to the second NMOS The source of tube S2 is connected.

In some embodiments, the autotransformer further includes a second resonant inductor. When the number of turns of the first transformer inductor is greater than 0, the second resonant inductor is connected in parallel with the first transformer inductor. When the number of turns of a transformer inductor is equal to 0, the second resonant inductor is connected in parallel with the second transformer inductor. Wherein, the second resonant inductor is an independent inductor or a magnetizing inductor of the transformer.

In some embodiments, when the number of turns of the first transformer inductor is greater than 0, the A transformer inductor includes at least one sub-transformer inductor, and the sub-transformer inductors are connected in series.

Referring to FIG. 1 , one end of the second resonant inductor Lm is connected to the same-name end of the first transformer inductor N1, and the other end of the second resonant inductor Lm is connected to the opposite-name end of the first transformer inductor N1.

FIG. 2 is a schematic circuit diagram of a non-isolated resonant converter in some embodiments of the present invention. The difference between Figure 2 and Figure 1 is that the number of turns of the first transformer inductor N1 is equal to 0, that is, the other end of the first resonant inductor Lr is directly connected to the source of the second NMOS transistor S2, so The second resonant inductor Lm is connected in parallel with the second transformer inductor N2, that is, one end of the second resonant inductor Lm is connected to the opposite end of the second transformer inductor N2, and the other end of the second resonant inductor Lm Connect to the same end of the second transformer inductor N2.

FIG. 3 is a schematic circuit diagram of a non-isolated resonant converter in other embodiments of the present invention. The difference between Figure 3 and Figure 1 is that both the fifth NMOS transistor S5 and the sixth NMOS transistor S6 are replaced with diodes.

FIG. 4 is a schematic circuit diagram of a non-isolated resonant converter in some embodiments of the present invention. The difference between Figure 4 and Figure 2 is that both the fifth NMOS transistor S5 and the sixth NMOS transistor S6 are replaced with diodes.

FIG. 5 is a timing diagram of the non-isolated resonant converter shown in FIG. 1 in some embodiments of the present invention. Referring to Figures 1 and 5, S ₁ represents the first control signal, S ₂ represents the second control signal, S ₃ represents the third control signal, S ₄ represents the fourth control signal, and S ₅ represents the fifth control signal, S ₆ represents the sixth control signal, I _Lr represents the current flowing through the first resonant inductor, I _Lm represents the current flowing through the second resonant inductor, IN _NS1 represents the current flowing through the first transformer inductor, and V _DS represents the current flowing through the first transformer inductor. Describe the voltage across the source and drain of the third NMOS transistor.

Referring to Figures 1 and 5, before time t0, the first NMOS transistor S1, the fourth NMOS transistor S4 and the fifth NMOS transistor S5 are turned on, and the second NMOS transistor S2 and the third NMOS transistor S2 are turned on. The transistor S3 and the sixth NMOS transistor S6 are turned off, and the turns ratio of the first transformer inductor Lr, the second transformer inductor N2 and the third transformer inductor N3 is n:1:1, n is greater than 0 , therefore, the voltage at both ends after the first resonant inductor Lr and the resonant capacitor Cr are connected in series is the resonant voltage, and the resonant voltage is equal to the difference between the power supply voltage V _in and (n+2) times the output voltage Vo. Under the excitation of the resonant voltage, the current I _{Lr flowing through the first resonant inductor Lr} rises according to the sinusoidal resonance and then decreases at resonance. The current I Lm flowing through the second resonant inductor _Lm is n times the output voltage Vo. Linearly increases under the action of One end flows into the first transformer inductor N1 through the same-name terminal of the first transformer inductor N1, and flows into the third transformer inductor N3 through the same-name terminal of the third transformer inductor N3. According to the working principle of the autotransformer , the second transformer inductor N3 will induce (n+1) times the current flowing through the first transformer inductor N1, and flow out from the same terminal of the second transformer inductor N2 and flow into the output capacitor Co One end of , that is, the current flowing through the second transformer inductor N2 and the current flowing through the third transformer inductor N3 jointly charge the output capacitor Co, and the total current is (n+2) times flowing through the third transformer inductor N3. The current of a transformer inductor N1 and the current flowing through the second resonant inductor N2 sum of currents.

Referring to Figures 1 and 5, at time t0, the first NMOS transistor S1, the fourth NMOS transistor S4 and the fifth NMOS transistor S5 are turned off, and the first resonant inductor Lr and the resonant capacitor Cr are connected. The direction of the current will not change suddenly. At this time, the direction of the current on the first resonant inductor Lr is positive, which will charge the junction capacitance of the first NMOS transistor S1 and the junction capacitance of the fourth NMOS transistor S4. At the same time, The junction capacitance of the second NMOS transistor S2 and the junction capacitance of the third NMOS transistor S3 is discharged, and the current that charges the junction capacitance of the first NMOS transistor S1 and the fourth NMOS transistor S4 still flows in. The current induced in the second transformer inductor N2 still flows from the same-name terminal of the third transformer inductor N3 through the different-name terminal. Therefore, although the fifth NMOS transistor S5 is turned off, the current still flows through the fifth NMOS transistor S5. The body diode of the NMOS transistor S5, and the current flowing through the body diode of the fifth NMOS transistor S5 is (n+1) times the current flowing through the first transformer inductor N1, and the junction of the second NMOS transistor S2. The sum of the capacitor discharge current and the junction capacitor discharge current of the third NMOS transistor S3.

Referring to Figures 1 and 5, at time t0 to t1, since the junction capacitance is very small, it can be considered that at this stage, the voltages across the source and drain of the first NMOS tube rise linearly, and the source of the fourth NMOS tube S4 The voltage across the source and drain of the second NMOS transistor S2 rises linearly, the voltage across the source and drain of the second NMOS transistor S2 linearly drops, and the voltage across the source and drain of the third NMOS transistor S3 drops linearly; After the voltage across the source and drain of the second NMOS transistor S2 and the voltage across the source and drain of the third NMOS transistor S3 drop to 0, the body diode of the second NMOS transistor S2 and the third NMOS transistor S3 The body diode of the NMOS transistor S3 is turned on, and the voltage across the source and drain of the second NMOS transistor S2 is And the voltage across the source and drain of the third NMOS transistor S3 is clamped at 0, and at the same time, the voltage at the source and drain of the fourth NMOS transistor S4 is clamped at the input voltage V _in and 2 times the The difference between the output voltage Vo; since no charging current flows through the fourth NMOS transistor S4, the current flowing through the third NMOS transistor S3 drops to 0, and at this time, the current flowing through the first resonant inductor Lr The current is greater than the current flowing through the second resonant inductor Lm. The current still flows into the second transformer N2 inductor from the opposite end of the second transformer inductor N2, and the current flowing through the second transformer inductor N2 is 2 times the difference between the current flowing through the first resonant inductor Lr and the current flowing through the second resonant inductor Lm. At this time, the second NMOS transistor S2 and the third NMOS transistor S3 are 0 voltage conduction.

Referring to Figures 1 and 5, at time t1 to t2, the body diode of the second NMOS transistor S2, the body diode of the third NMOS transistor S3, and the body diode of the fifth NMOS transistor S5 are conductive. When a resonant inductor Lr and the resonant capacitor Cr are connected in series, the resonant voltage at both ends is equal to the sum of the power supply voltage V _in and n times the output voltage Vo. Under the action of the resonant voltage, the first resonant inductor Lr flows through and the current of the resonant capacitor Cr drops rapidly, and the current flowing into the first transformer inductor N1 is equal to the difference between the current flowing through the first resonant inductor Lr and the current flowing through the second resonant inductor Lm , when the current flowing through the first resonant inductor Lr is equal to the current flowing through the second resonant inductor Lm, the current flowing through the second transformer inductor N2 drops to 0, and at this time, the current flowing through the first resonant inductor Lm All the current of the resonant inductor Lr flows through the body diode of the fifth NMOS transistor S5, and the resonance state of the circuit remains unchanged. Therefore, the current flowing through the first resonant inductor Lr and the resonant capacitor Cr is at the resonant voltage. The effect of The current part of the second resonant inductor Lm flows into the opposite terminal of the first transformer inductor N1, and the second transformer inductor N2 induces a current and flows out from the opposite terminal. Considering that the second resonant inductor N2 The inductance value is relatively large. During this period, the current change on the second resonant inductor Lm is ignored. As the current on the first resonant inductor Lr decreases, the current flowing into the opposite end of the first transformer inductor N1 gradually increases. , the current induced by the second transformer inductor N2 gradually increases. At this time, the current flowing through the third NMOS transistor S3 is the current flowing through the first resonant inductor Lr, and at the same time, the current flowing through the third resonant inductor Lr. The sum of the current flowing through the body diode of the fifth NMOS transistor S5 and the current flowing through the second transformer inductor N2, as the current flowing through the second transformer inductor N2 gradually increases, the current flowing through the fifth NMOS transistor S5 The current gradually becomes smaller until time t2, when the current flowing through the fifth NMOS transistor S5 drops to 0, and the current flowing out of the opposite end of the second transformer inductor N2 is equal to the current flowing through the first resonant inductor Lr. , the fifth NMOS transistor S5 is turned off.

Referring to Figures 1 and 5, at time t2 to t3, at time t2, the fifth NMOS transistor S5 has just turned off, and the voltages across the source and drain of the fifth NMOS transistor S5 are 0. Therefore, the fifth NMOS transistor S5 When a resonant inductor Lr and the resonant capacitor Cr are connected in series, the resonant voltage at both ends is equal to the sum of the power supply voltage V _in and n times the output voltage Vo. Under the action of the resonant voltage, the first resonant inductor Lr and the resonant capacitor Cr flow through the first resonant inductor Lr and the resonant capacitor Cr. The current of the resonant capacitor Cr decreases rapidly, the current flowing into the opposite terminal of the first transformer inductor N1 increases, the current flowing out of the opposite terminal of the second transformer inductor N2 increases accordingly, and the current flowing through the second transformer inductor N2 The junction capacitance of the fifth NMOS transistor S5 is greater than the current flowing through the first transformer inductor N1, and the current flowing through the second transformer inductor N2 is greater than the current flowing through the first transformer inductor N1. charge so that the source and drain of the fifth NMOS transistor S5 The voltage across the terminals increases. According to the coupling relationship of the autotransformer, the junction capacitance of the sixth NMOS transistor S6 begins to discharge, and the voltage across the source and drain of the sixth NMOS transistor S6 begins to decrease. The first After the resonant inductor Lr and the resonant capacitor Cr are connected in series, the resonant voltage at both ends gradually decreases. Until time t3, the voltage at the source and drain of the sixth NMOS transistor S6 drops to 0. The body diode is turned on, clamping the voltage across the source and drain of the sixth NMOS transistor S6 at 0. During this process, the resonant voltage at both ends of the first resonant inductor Lr and the resonant capacitor Cr gradually decreases until the resonant voltage at both ends of the first resonant inductor Lr and the resonant capacitor Cr is connected in series at time t3. The sixth NMOS transistor S6 is clamped to the difference between the power supply voltage _Vin and (n+2) times the output voltage Vo. At this time, the sixth NMOS transistor S6 is turned on at 0 voltage.

Referring to Figures 1 and 5, after time t3, the resonant voltage at both ends after the first resonant inductor Lr and the resonant capacitor Cr are connected in series is between the power supply voltage V _in and (n+2) times the output voltage Vo. Difference, under the excitation of the resonant voltage, the currents in the first resonant inductor Lr and the resonant capacitor Cr first rise according to sinusoidal resonance and then fall through the resonance, and the current flowing through the second resonant inductor Lm is n times The output voltage Vo increases linearly under the action of the output voltage Vo. The sine wave current on the first resonant inductor Lr flows through the second NMOS transistor S2, flows into the opposite terminal of the first transformer inductor N1, flows through the The third NMOS transistor S3 flows into the opposite end of the second transformer inductor N2 and outputs it to one end of the output capacitor Co. Since the current of the first transformer inductor N1 and the current of the second transformer inductor N2 are both determined by The opposite end flows in. According to the working principle of the autotransformer, the third transformer inductor N3 induces (n+1) times the electric current flowing through the first transformer inductor N1. flows and flows out from the opposite terminal, and together with the current of the first transformer inductor N1 and the current of the second transformer inductor N2, flows into one end of the output capacitor Co, that is, the current flowing through the second transformer inductor N2 Together with the current flowing through the third transformer inductor N3, the output capacitor Co is charged. The total current is (n+2) times the current flowing through the first transformer inductor N1 and the current flowing through the second resonance. The sum of the currents on the inductor Lm. The subsequent process is a repetitive process with the same principle and will not be described in detail here.

In this application, the switching frequency of the non-isolated resonant converter is higher than the resonant frequency of the first resonant inductor and the first two capacitors, or the switching frequency of the non-isolated resonant converter is lower than the first resonant capacitor. The resonant frequency of the resonant inductor and the first and second capacitors, each switching unit adopts a controllable switching device or an uncontrollable switching device, and the working characteristic path changes slightly. Workers in the field can deduce the specific working mode, which will not be discussed here. Go into details.

In this application, the turn-on and turn-off of the first NMOS transistor, the second NMOS transistor, the third NMOS transistor and the fourth NMOS transistor cause the first resonant inductor and the resonant capacitor to It works in resonance with the second resonant inductor to form a resonant current. The resonant current flows into the first transformer inductor and simultaneously flows into the second transformer inductor or the third transformer inductor, and flows into the third transformer where no current flows. An induction film is formed in the inductor or the second transformer inductor, and through the freewheeling effect of the fifth NMOS tube or the sixth NMOS tube, the current flows from the same terminal of the second NMOS tube and the third NMOS tube. The ends of the tubes with the same name flow out at the same time, so that the total current injected into one end of the output capacitor and one end of the load is proportionally distributed to the second transformer inductor and the third transformer inductor, reducing the current on the transformer inductor. Valid values. For example, the resonant current formed by the resonant operation of the first resonant inductor, the resonant capacitor and the second resonant inductor flows into the same-name terminal of the first transformer inductor. At this time, the current flows into the same-name terminal of the third transformer inductor. Through the coupling effect of the autotransformer, a current is induced in the second transformer inductor and passes through the The current flowing out of the same terminal of the second transformer inductor and the sum of the resonant currents of the first resonant inductor, the resonant capacitor and the second resonant inductor flow into the output capacitor. one end and one end of the load, converting the input DC voltage into the output voltage.

By utilizing the resonant operation of the first resonant inductor, the resonant capacitor and the second resonant inductor, soft switching of all switching units can be achieved; by adjusting the switching frequency of the non-isolated resonant converter, the output voltage can be adjusted Adjustment; by adjusting the turns ratio of the autotransformer, the output voltage can be changed, thereby achieving non-isolation, input-output voltage conversion at high efficiency; utilizing the relationship between voltage and current in the autotransformer, the autotransformer current can be reduced The effective value of , improves the efficiency of the non-isolated resonant converter.

Although the embodiments of the present invention have been described in detail above, it will be obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes are within the scope and spirit of the invention as described in the claims. Furthermore, the invention described herein is capable of other embodiments and of being practiced or carried out in various ways.

Claims (13)

1. A non-isolated resonant converter, characterized in that it includes a first resonant bridge, a second resonant bridge, a freewheeling tube unit, a resonant network, an autotransformer, a load and an output capacitor, and the autotransformer includes a first transformer inductor , the second transformer inductor and the third transformer inductor, the resonant network and the first transformer inductor are connected in series to form a transformer resonant unit, the first end of the transformer resonant unit is connected to the first resonant bridge, the The second end of the transformer resonant unit is connected to the second resonant bridge, and the same-name end of the second transformer inductor is connected to the different-name end of the third transformer inductor, one end of the output capacitor, and one end of the load, The opposite end of the second transformer inductor is connected to the first resonant bridge and the freewheeling tube unit, and the same end of the third transformer inductor is connected to the second resonant bridge and the freewheeling tube unit. , the first resonant bridge and the second resonant bridge are also connected to the positive electrode of the power supply, the freewheeling tube unit is connected to the other end of the output capacitor and the other end of the load and grounded, the first The resonant bridge is used to connect the first end of the transformer resonant unit with the positive pole of the power supply or the freewheeling tube, and the second resonant bridge is used to connect the second end of the transformer resonant unit with the positive pole of the power supply or the freewheeling tube. The freewheeling tube is connected, and the freewheeling tube is used to connect the different end of the second transformer inductor or the same end of the third transformer inductor with the other end of the load, wherein the first transformer inductor The number of turns is greater than or equal to 0.
2. The non-isolated resonant converter according to claim 1, wherein the first resonant bridge includes a first switch unit and a third switch unit, the first terminal of the first switch unit is connected to the positive electrode of the power supply, so The second end of the first switch unit is connected to the first end of the third switch unit, and the second end of the third switch unit is connected to the second transformer inductor. The heteronymous end connection.
3. The non-isolated resonant converter according to claim 2, wherein both the first switching unit and the third switching unit are controllable switching devices.
4. The non-isolated resonant converter according to claim 1, wherein the second resonant bridge includes a second switch unit and a fourth switch unit, the first terminal of the second switch unit is connected to the positive electrode of the power supply, so The second end of the second switch unit is connected to the first end of the fourth switch unit, and the second end of the fourth switch unit is connected to the same end of the third transformer inductor.
5. The non-isolated resonant converter according to claim 4, wherein both the second switching unit and the fourth switching unit are controllable switching devices.
6. The non-isolated resonant converter according to claim 1, wherein the freewheeling tube unit includes a fifth switching unit and a sixth switching unit, and the first end of the fifth switching unit is connected to the second transformer. The opposite end of the inductor is connected, the second end of the fifth switching unit is connected to the other end of the load, the first end of the sixth switching unit is connected to the same end of the third transformer inductor, the The second end of the sixth switching unit is connected to the other end of the load.
7. The non-isolated resonant converter according to claim 6, wherein the fifth switching unit and the sixth switching unit are both uncontrollable switching devices or controllable switching devices.
8. The non-isolated resonant converter according to claim 3, 5 or 7, characterized in that the controllable switching device includes a metal oxide semi-field effect transistor, an insulated gate bipolar transistor, a gallium nitride transistor, a silicon carbide MOS tube and a first combined switch unit, the first combined switch unit is a combination of a triode and a diode.
9. The non-isolated resonant converter according to claim 7, wherein the uncontrollable switching device includes a diode and a second combined switch unit, and the second combined switch unit includes a diode, a metal oxide semi-field effect transistor, an insulating A combination of any one of gate bipolar transistors, gallium nitride transistors, and silicon carbide MOS transistors.
10. The non-isolated resonant converter according to claim 1, wherein the resonant network includes a first resonant inductor and a resonant capacitor, and the first resonant inductor, the resonant capacitor and the first transformer inductor are connected in series.
11. The non-isolated resonant converter according to claim 10, wherein the resonant network further includes a resistor, the resistor is connected in series with the first resonant inductor, the resonant capacitor and the first transformer inductor.
12. The non-isolated resonant converter according to claim 1, wherein the autotransformer further includes a second resonant inductor, and when the number of turns of the first transformer inductor is greater than 0, the second resonant inductor and The first transformer inductor is connected in parallel. When the number of turns of the first transformer inductor is equal to 0, the second resonant inductor is connected in parallel with the second transformer inductor.
13. The non-isolated resonant converter according to claim 1, characterized in that when When the number of turns of the first transformer inductor is greater than 0, the first transformer inductor includes at least one sub-transformer inductor, and the sub-transformer inductors are connected in series.